Diamond lap



March 26, 1940. L. W. GOD DU ET Al.

DIAMOND LAP Filed Nov. 4, 1937 2 Sheets-Sheet l w H A Flam P151? FIZZ HNTOR WE/GHTON GODDU SZg ZL ATTORNEY FIB.

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LLOYD w BY Wei/211% March 26, 1940. L. w. GODDU ET AL 2,194,546

numoun LAP Filed'Nov. 4, 1931' 2 Sheets-Sheet 2 FIE. II FIE. I

FIEJI Ham INVENTOR WILL/0M J. WIEIGHTON LLOYD W GODDU I mond'particlesin the wiremesh;

Patented Mar. 26, 1940 UNITED STATES.

DIAMOND LAP Lloyd W. Goddu and William :1. Wrighton,

I Southbridge, Mass, assignors' to American ptical Company, Southbridge,Mass, a voluu-y tary association of Massachusetts Application November4, 937, Serial No.1'l2,800 3 Claims; (Cl. 51-278) This invention relatesto diamond laps and to a method for making the same.

.An object of the inventionis to improve the wearing qualities of thediamond laps thus produced. I

In the accompanying drawings which illustrate our invention Fig. I is aperspective view of a diamond lap; Fig. II is a plan view of sheet metalcarryin the diamond particles;

Fig. III is an end view illustrating the assembly of such a sheet with acore;

hating of" wire mesh with diamond particles;

.Fig.-VI is a detail sectional view on-an .enlarged scaleillustratingthe fixing of the dia- Fig. VII is a diagrammatic sectional viewillustrating the insertion of the diamond impregnated mesh in the lap;,'

, Fig. vm isf'a view similar. to'Fig. IV illustrat- I ing the insertionof adiamond carrying mixture' into the lap;

' Fig. IX is a plan view of wire mesh impregna'ted with diamondparticles; Fig. X is a plan view of a lap having a plurala ity of layersof diamond impregnated meshset into the body of the lap;

Fig. XI is a sectional view on the line XI-XI of Fig. X;

Fig. XII is a plan view of a lap having diamond 35 impregnated meshapplied as a surface layer thereon; and

Fig. XIII -is a sectional view on the' line XIIL-XIII of Fig. XII.

In abrading devices such as laps which em- 40 ploy diamond particles asthe, cutting agent to I do the abrading, the diamond particles are heldor embedded in a material which gradually wears down as abradingproceeds. For the sake of economy the diamond particles should be firmlyIn accordance with our invention, we seembed the diamond particles-thatas the matrix in which they are embedded gradually wears down they areall held, from first to last, with substantially the same degree oftenacity. This 5 means that a diamond particle of the samjesizeRockwell, which is the range Lof-hardness generally found suitable fordiamond laps.

and sharpness: is maintained in operative position for substantiallythesame length of time, no matter whether thisparticleis reached towardsthe beginning or towards the end of the life of the abrading' tool as awhole. Q In Fig. I, wehave conventionally illustrated a diamond lap suchas employed for grinding glass to a predetermined spherical surface. Thebody Ill ofthe lap is generally of copper or steel which is soft enoughto wear down as the dia- I.

mlond particles'become used up, but is durable v enoughto provide asuitable mounting for the Fig. IV is a diagrammatic sectionalview'illustrating the-insertionoff the diamond carrying .15 metal intothe body of the lap;

Fig. V is a plan view illustrating the impregparticles so long as theiruseful cutting-life lasts. Inaccordance with our invention'we' form amultiplicity'ofdepressions in the body l0, then :0

insert abrasive carrying metalin these depressions and soften-.theinserted metal by heating,

in this way settlingutheiinserted metal into the depressions to form anintegral part of the lap.

In the particular embodiment of our inven- '9 tion illustrated "inFigs,- II, III and IV, we use sheet copper for carrying the diamondparticles.

Fig. II is a plan view showing the diamond particles which have beencaused in any suitable fashion to adhere to the face of the sheet cop-3| per. ii.

'We then fold the diamond carrying sheet of copper I I' about the corei2 of soft iron. This core is selected in suitable dimensions forwedging the sheet H in one of a multiplicity of kerfs 39 I4 formed inthe lap l0 as diagrammatically illustrated in Fig. IV. It will be notedthat the diamond particles are not dislodged from the sheet copper I'lduring the inserting step because the particles are firmly held betweenthe copperv and the soft iron core.

The kerfs are thus charged with the abrasive carrying metal; and thekerfs are preferably evenly distributed about the body of the lap so asto give a uniform grinding action. The lap is then heat treated underreducing conditions and raised to a temperature sufiiciently high tosoften or melt the 1 copper. It is desirable to carry on this heattreatment in a reducing atmosphere, butreducing conditions can be ob- 5tained in other waysif found more desirable. The whole'is then quenched.from about 1500 to 1600 F. to give the steel temper. The latter is thendrawn to about 25 to 40 on the C. ,scale,

treatment hardens the steel suiiiciently so that it does notwear downrapidly enough to release the diamond particles before their useful lifeis finished. The diamond particles are emdiamond particles may bebrushed over wire wesh l6, preferably of alloysteel wire which willresist softening at the temperature used for softening the copper. Weselect the mesh l6 according to the size of the diamond particles, forinstance,

100 mesh. When the diamond particles are brushed over the wire mesh,each of the interstices receives a diamond particle so that theseparticles are quite uniformly distributed.

We find it advantageous to deposit a flash coating of copper over thealloy steel wire before the diamond particles are distributed in theinterstices. We then plate the diamond impregnated wire mesh with copperl'l, so as to fix the diamond particles in-the wire mesh in the mannerillustrated in Fig. VI. The abrasive carrying mesh I6 is protected onone or both sides with sheet copper l8, then folded together ina-plurality of layers to make up an insert l9, which is pushed intoakerf M in the manner indicated in Fig. VII.

The lap is then heat treated under reducing conditions to melt or softenthe copper, as set forth in connection with the first embodiment of ourinvention. Here the wire mesh serves to hold the diamond particles fromrising to the surface and thus becoming segregated, while the copper isin softened condition; and therefore the diamond abrasive is uniformlydistributed through-.

out the kerf l4. When the copper hardens again the particles areembedded in a matrix which tenaciously holds the diamond particles asthe lap is gradually worn away to expose the underlying particles ofabrasive. The lap is quenched and drawn in the manner set forth inconnection with the first embodiment of the invention, to control therate at which the lap wears away.

Fig. VIII illustrates a further modification of our invention inaccordance with which a mixture of diamond dust and copper or brassparticles or chips is forced into each kerf 14. If a brass is used, weprefer to use a brazing brass. After the copper and diamond particles orbrass and diamond particles have been carefully mixed, the mixture isforced into the kerfs H. The lap is then heat treatedunder reducingconditions to sinter the particles of metal together. In this sinteringoperation the diamond carrying metal becomes moulded to the contour ofthe recess ll in which the metal is received. The body III of steel isthen quenched and drawn in the manner set forth in connection with thefirst embodiment of our invention. 9

Control of the heat treating temperature so as not to render the copperor brass liquid, but rather to sinter the metal particles together.makes it impossible for the diamond particles to segregate out of themetal during the heat treatment.

A further modification of our invention is illustrated in Figs. IX, Xand XI; and here the body Illa of the lap is provided with an annulargroove 22 for receiving a plurality of layers of diamond impregnatedmesh. One of the inserts 23 of diamond impregnated wire mesh is shown inFig. IX. We prefer to impregnate the wire mesh with the diamondparticles and secure the particles in place by the aid ofelectrolytically deposited copper as described in connection with Figs.V and VI of the drawings. Here the wire mesh is in the shape of anannulus which is of such size as to fit into the groove 22. Thesuccessive layers of in a depression, groove, or the like, as set forthin connection with Figs. VII, and XI, we may apply the impregnated wiremesh to the surface of the lap which is used in abrading. Figs. XII andXIII illustrate this modification of our invention.

The diamond impregnated wire mesh is prepared as set forth in connectionwith Figs. V, VI and VII. The wire mesh is in the shape of an annulusand is applied to the rounded annular shoulder or rim 26 of the lap asillustrated in Fig. XIII. The edges of the annulus are pressed down sothat the wire mesh conforms to the contour of the shoulder and liessnugly against the surface thereof. The lap is then heat treated underreducing conditions to melt or soften the copper as set forth inconnection withthe preceding embodiments of our invention. As copperdiffuses into steel below the softening point of the latter, anexcellent bond is thus efi'ected between the'diamond impregnated wiremesh and the steel lap. This results in a surface layer of abrasive inwhich the diamond particles are embedded in copper, the latter beingreinforced by steel wire mesh. Inasmuch as the diamond particles aredisposed in the interstices of the wire mesh, the diamond particles areeach in efiect provided with a setting or mounting which affords amplesupport during the abrading operation until the useful life of thediamond particles is spent.

This latter is an important advantage from the point of view of economy.We have discovered that even with a matrix material which isparticularly well adapted for retaining the diamond particles duringgrinding, the particles are inefficiently held if two or more of themare held in a single pocket. In other words, the matrix or embeddedmaterial must completely surround each individual particle so that eachhas its own setting or pocket. The use of the wire mesh into which thediamond particles are brushed is particularly advantageous in insuringthat the individual particles are spaced apart and each tenaciously heldby its own setting.

The procedure taught herein insures remarkable uniformity in the cuttingoperation throughout the life of the abrading device, thus promotingeconomical use of the diamond particles.

While we have illustrated and described certain embodiments of ourinvention, it will be understood that the invention may be otherwiseembodied and practiced within the scope of the fol lowing claims.

We claim:

1. In a method of producing an abrading device, the steps conslsting informing a slot in' the device, dispersing abrasive particles amonglayers of metal softe'nable at a lower temperature than said slotteddevice, inserting saidabrasive carrying layers of metal in a slot ofsaid device, and softening the metal with heat after such insertion soas to cause it to conform more nearly to the cross section of said slot.

2. In a method of producing an abrading device, the steps consisting informing a narrow depression in the device, folding sheet metal toinclude abrasive particles and form an insert,

placing said insert in the depression in said device, and softening themetal with heat after such insertion so as to cause it to conformsubstantial- 10 1y to the cross-section of said depression.

LLOYD W. GODDU.

WILLIAM J. WRIGHTON. 1o

